Unit 2 - Bonding, structure and properties of matter Flashcards
(26 cards)
What is metallic bonding?
Bonds between metal atoms, creating a lattice of ions surrounded by a sea of delocalised electrons.
How do metals conduct electricity/heat?
The delocalised electrons are free to move throughout the structure
What is ionic bonding?
Bonds between metal and non-metal atoms. Metal atoms donate electrons to non-metals to form ions. Metals always end up with an empty outer shell, non-metals end up with a full (8 electrons) outer shell.
What must the charges of all ions in an ionic compound sum to?
Zero
What happens if the charges are not equal?
More atoms of the element which is uneven is needed. For example, Beryllium loses 2 electrons, while chlorine only gains 1. This means there must be an extra chlorine atom to balance the +2 charge of beryllium ions. This makes the formula for beryllium chloride BeCl2.
What is covalent bonding?
Bonds between non-metal atoms. Electrons are shared between atoms to gain a full outer shell. Every covalent bond exists of a pair of shared electrons
What are ionic structures/compounds composed of?
Ions arranged in a lattice of repeating units of positive and negative ions, forming a crystal.
What are some properties of ionic substances?
-They have high melting points due to strong ionic bonds (ions have strong electrostatic forces of attraction
-They can conduct electricity when in liquid form - molten or in solution (dissolved) - because in these states ions are free to move and carry charge
What is another name for ionic compounds?
Salts - such as sodium chloride - are always made and named from the positive metal ion (cation) and the negative ion (anion)
What are the formulas for molecular ions?
Hydroxide (alkali) ion = OH⁻
Sulphate ion = SO42⁻
Carbonate ion = CO3(2-)
Nitrate ions = NO⁻ ₃
Ammonium ion = NH₄⁺
How do we name ionic compounds (salts)?
The metal ion (cation) followed by the non-metal ion (anion)
What are simple covalent structures?
Molecules formed through covalent bonding (sharing electrons).
What are the boiling points of simple covalent structures and why?
Simple covalent structures have low boiling points due to weak intermolecular forces that need to be overcome
What is giant covalent bonding?
Similar to ionic lattice. Atoms form covalent bonds to other atoms, which form bonds to other atoms and so on until a giant molecule is formed. An example is diamond, a crystal of carbon atoms bonded covalently
What are properties of giant covalent structures?
Very high melting points, as you have to overcome covalent bonds between atoms
What is an allotrope of carbon?
Different structural forms of carbon, exhibiting different physical properties despite being composed of the same element
What are some allotropes of carbon?
-Diamond
-Graphite
-Graphene
-Fullerenes
What is graphene?
A single layer of graphite
What are fullerenes?
3D structures of carbon atoms, such as Buckminster fullerene. Nanotubes are tube-shaped fullerenes
What are some properties of graphite?
-Delocalised electrons form weak bonds, so it can conduct electricity as electrons can move between layers
-Layers can slide past each other, making it soft (unlike alloys)
Why are alloys stronger than pure elements?
The mixture of elements means there are different sized atoms, which causes the layers of the lattice to be disrupted, so they cannot slide
How big are coarse particles e.g. dust?
Larger than 2500nm
How big are fine particles?
100 - 2500 nm
How big are nanoparticles?
Less than 100nm
